Pumping  unit

ABSTRACT

In the pumping unit disclosed, the friction acting on the impeller is reduced, and the efficiency is increased by at least two adjacent indentations of at least one face end of the impeller and/or of the at least one end wall of the pump chamber communicate with one another via a respective groove.

PRIOR ART

The invention is based on a pumping unit as generically defined by the preamble to the main claim. A pumping unit is already known from European Patent Disclosure EP 1 091 127 A1, with an impeller which is disposed in a pump chamber and is drivable to rotate by means of an actuator and has two face ends, diametrically opposite each of which is a respective end wall of the pump chamber, and a plurality of indentations for hydrodynamic support in both face ends of the impeller. A disadvantage is that dirt particles can collect in the indentations. If the dirt particles are flushed out of the indentations, they cause increased friction in the region between the annularly disposed indentations and hence cause scratches, since the axial gap there between the impeller and the pump chamber is smaller than the region of the indentations.

ADVANTAGES OF THE INVENTION

The pumping unit of the invention having the definitive characteristics of the body of the main claim has the advantage over the prior art that in a simple way, an improvement is obtained such that at least two adjacent indentations of the at least one face end and/or of the at least one end wall communicate with one another via a respective groove. In this way, the axial gap in the region between the indentations is increased in size, so that the dirt particles cannot cause increased friction and scratches there.

By the provisions recited in the dependent claims, advantageous refinements of and improvements to the pumping unit defined by the main claim are possible.

In an advantageous version, the indentations and grooves are disposed annularly and extend in arclike, split-ringlike, oblong slot-like or similar form. The indentations and the grooves are advantageously disposed on a common ring.

It is furthermore advantageous if the indentations have a greater depth than the grooves, since in this way oblique faces can be embodied that achieve a hydrodynamic support of the impeller.

It is especially advantageous that the indentations each have at least one face that is oblique with respect to the face ends and/or the end walls, for hydrodynamic support of the impeller, since in this way the axial position of the impeller is adjusted such that the two axial gaps between the impeller and the end walls of the pump chamber are at least nearly the same size. As a result, the friction acting on the impeller is reduced, and the efficiency of the pumping unit is increased. The at least one oblique face, when the indentations are disposed on the impeller, is each provided on a trailing end of the indentation relative to a direction of rotation of the impeller, and when the indentations are disposed on the end walls of the pump chamber, is each provided on a downstream end of the indentation.

It is also advantageous if the indentations each have a lowest point that extends parallel to the at least one face end and/or end wall.

It is moreover advantageous if the indentations of one face end of the impeller are diametrically opposite the indentations of the other face end of the impeller mirror-symmetrically relative to a middle face, and the indentations that are diametrically opposite mirror-symmetrically are joined together via a pressure equalization conduit. In this way it is attained that the pressure in the two indentations joined via the pressure equalization conduit is equalized.

DRAWINGS

Exemplary embodiments of the invention are shown in simplified form in the drawings and described in further detail in the ensuing description.

FIG. 1, in section, shows a fragmentary view of the pumping unit of the invention;

FIG. 2 shows an impeller of the pumping unit;

FIG. 3 is a sectional view of the impeller taken along the line III-III in FIG. 2;

FIG. 4 is a sectional view of the pumping unit taken along the line indentation-IV in FIG. 1;

FIG. 5 is a sectional view of the pumping unit taken along the line V-V in FIG. 1 in a second exemplary embodiment; and

FIG. 6 is a sectional view with the impeller and with indentations, disposed in an end wall of the pump chamber, in accordance with the second exemplary embodiment.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a pumping unit of the invention.

The pumping unit of the invention serves to pump a fluid, such as fuel, from a supply container to an internal combustion engine, for instance via a pressure line.

The pumping unit of the invention is embodied as a flow pump, such as a peripheral pump or lateral channel pump, and has a pump housing 1 which has a pump part 2 and a motor part 3.

The pump part 2 has a pump chamber 4, in which an impeller 5 revolves as it rotates about a rotationally symmetrical pump axis 8. The impeller 5 is driven by an actuator 9, provided in the motor part 3, via a drive shaft 10. The actuator 8 is an electric motor, for instance, and is disposed in a motor compartment 7 of the motor part 3.

A region upstream of the pump chamber 4 is called the intake side, and a region downstream of the pump chamber 4 is called the compression side of the unit.

The pump chamber 4 has a pump chamber inlet 11 and a pump chamber outlet 12. The pump chamber 4 is defined by two end walls diametrically opposite one another in the direction of the pump axis 8, that is, a first end wall 15 and a second end wall 16, the pump chamber inlet 11 being provided in the first end wall 15 and the pump chamber outlet 12 being provided in the second end wall 16, and is defined in the radial direction relative to the pump axis 8 by an annular wall 17.

The impeller 5 has a plurality of impeller blades 5.1, and a blade chamber 5.2 is formed between blades. The blade chambers 5.2 are open toward the end walls 15, 16 and are closed radially outward for instance relative to the pump axis 8 by a ring 5.3, which is disposed on the radially outer ends of the impeller blades 5.1. However, the blade chambers 5.2 may expressly also be open radially outward and not have any ring 5.3.

Annular feed conduits 14 are disposed in the end walls 15, 16, in the radial region of the impeller blades 5.1.

The first end wall 15 is part of an intake cap 18, for instance, and the second end wall 16 and the annular wall 17 are for instance part of a pressure cap 19. An inlet conduit 22 is provided in the intake cap 18 and discharges into the pump chamber 4 via the pump chamber inlet 11; the fluid pumped by the pumping unit leaves the pump chamber 4 via the pump chamber outlet 12. The pump chamber 4 communicates fluidically with the motor compartment for instance via the pump chamber outlet 12 and an outlet conduit 23 that is provided in the pressure cap 19.

The pressure cap 19 has a through opening 24. The drive shaft 10, mechanically coupled with the actuator 9, begins at the motor compartment 7 and protrudes through the through opening 24 of the pressure cap 19 into the pump chamber 4.

The axial width of the pump chamber 4 is greater than the axial width of the impeller 5, so that one axial gap 20 each approximately ten to thirty micrometers wide exists between the impeller 5 and the respective end walls 15, 16. The difference between the width of the pump chamber 4 and the width of the impeller 5 is defined as the total axial gap.

The impeller 5 is slipped for instance onto the drive shaft 10 protruding into the pump chamber 4; for this purpose, the impeller 5 has an impeller opening 25, into which the drive shaft 10 at least protrudes so as to be connected to the impeller by positive and/or nonpositive engagement. The impeller 5 is supported on the drive shaft 10 for instance in such a way that it is movable axially between the first end wall 15 and the second end wall 16.

The impeller 5 has a first face end 28, which is oriented toward the first end wall 15 of the pump chamber 4, and a second face end 29, which is oriented toward the second end wall 16 of the pump chamber 4.

In at least one of the face ends 28, 29 of the impeller 5 and/or at least one of the end walls 15, 16 of the pump chamber 4, a plurality of indentations 38 are provided, for hydrodynamic support of the impeller 5. In FIG. 1, the indentations 38 are disposed for instance on the face ends 28, 29 of impeller 5. However, in a second exemplary embodiment, they may instead be provided on the end walls 15, 16 of the pump chamber 4. The indentations 38 are embodied in such a way that they act like a hydrodynamic bearing and in this way adjust the axial position of the impeller 5 between the first end wall 15 and the second end wall 16 of the pump chamber in such a way that two equal-sized axial gaps 20 are created between the impeller 5 and the end walls 15, 16. As a result, only slight forces of friction act on the impeller 5, so that the efficiency of the pumping unit is improved.

The pumping unit aspirates fluid, for instance, from a supply container 32 via an inlet conduit 22, the pump chamber inlet 11, the pump chamber 4, the pump chamber outlet 12, the outlet conduit 23, and the motor compartment 7 of the motor part of the pump housing 1, and pumps the fluid, such as fuel, via a pressure line 33, to an internal combustion engine 34, for instance. In the pressure line 33, a check valve 35, for instance, is provided in order to maintain a predetermined pressure in the pressure line 33 after the pumping unit has been shut off.

FIG. 2 shows an impeller of the pumping unit with indentations in a first exemplary embodiment of the pumping unit of the invention.

In the impeller of FIG. 2, the elements that remain or function the same as in the pumping unit of FIG. 1 are identified by the same reference numerals.

The indentations 38 are provided for instance radially inside the impeller blades 5.1 of the impeller 5 and are disposed located on an imaginary circular ring. The ring is provided centrally, for instance, relative to the pump axis 8. By way of example, four indentations 38 are distributed uniformly over the circumference of the ring. However, it is expressly possible for an arbitrary number of indentations 38 to be provided. The indentations 38 extend for instance in arclike, split-ringlike, oblong slot-like or similar form. The indentations 38 each have one face 39 that is oblique relative to the face ends 28, 29 for the sake of hydrodynamically supporting the impeller 5. The oblique face 39 for hydrodynamic support is disposed on a trailing end of the indentation 38, with respect to a direction of rotation 31 of the impeller 5. Each of the indentations 38 has a lowest point 40 that extends for instance parallel to the face ends 28, 29. By way of example, the lowest point 40 of the indentations 38 is adjacent to two oblique faces 39, one leading and the other trailing. In the first exemplary embodiment, the leading oblique face 39 has a shorter length, for instance a shorter arc length, than the oblique face 39 that is trailing in the direction of rotation. The oblique face 38 leading in the direction of rotation may also be omitted and replaced with a steplike shoulder, since it makes no contribution to the hydrodynamic support.

According to the invention, at least two adjacent indentations 38 of the at least one face end 28, 29 and/or of the at least one end wall 15, 16 communicate with one another via a respective groove 42. In the first exemplary embodiment, both face ends 28, 29 of the impeller 5 are provided with indentations 38. For example, each indentation 38 communicates with the respective adjacent indentation 38 via a groove 42. The grooves 42 extend for instance in arclike, ringlike or similar for, so that the indentations 38 and the grooves 42 together form one common ring. The indentations 38 and grooves 42, however, remain different at least in the respect that the depth of the grooves 42 is less than the depth of the lowest point 40 and of the oblique faces 39 of the indentations 38 (FIG. 3). The width Bn of the grooves 42, measured in the radial direction with respect to the pump axis 8, is for example equal to the width Bv, measured radially with respect to the pump axis 8, of the indentations 38, but may also be different.

The oblique faces 39 of the indentations 38 are formed by the provision that the pressure equalization conduits of the indentations 38, beginning from the lowest point 40 of each, to the adjacent groove 42 decreases, for instance continuously.

FIG. 3 shows a sectional view of the impeller taken along the line III-III in FIG. 2.

In the region of the lowest point 40, the indentations 38 extend for instance approximately parallel to the face ends 28, 29. After that, viewed counter to the direction of rotation 41, they extend along a trailing oblique face 39, with a reduction in the depth, in the direction of a trailing groove 42 in terms of the direction of rotation 41 and discharge into this groove. Viewed in the direction of rotation, the depth of the indentation 38 decreases, either via a steplike shoulder 43 shown in dashed lines or via a leading oblique face 39 and discharges into a leading groove 42.

The indentations 38 of one face end 28 of the impeller 5 are diametrically opposite the indentations 38 of the other face end 29 of the impeller 5, for instance mirror-symmetrically relative to a middle face 45, and the indentations 38 diametrically opposite one another mirror-symmetrically communicate with one another via a pressure equalization conduit 46. In this way, an equally high pressure builds in both of the indentations 38 that communicate via the pressure equalization conduit 46. The pressure equalization conduit 46 discharges into the indentation 38 for instance in each case in the region of the lowest point 40.

The fluid located in the axial gap 20 is entrained in the direction of rotation 41 upon the rotation of the impeller 5 and has a relative speed oriented counter to the direction of rotation 41 with respect to the impeller 5. The fluid in the axial gap 20 therefore flows through the indentations 38 and the grooves 42 counter to the direction of rotation 41. In the region of the trailing oblique face 39, the flow cross section narrows in wedgelike form between the face ends 28, 29 of the impeller 5 and the end walls 15, 16 of the pump chamber 4, so that an increasingly higher pressure in the fluid builds up and acts on the respective face end 28, 29 of the impeller 5 and in this way adjusts the axial position of the impeller 5 in such a way that axial gaps 20 of equal size result.

FIG. 4 is a sectional view of the pumping unit taken along the line indentation-IV in FIG. 1 and FIG. 5 is a sectional view of the pumping unit taken along the line V-V in FIG. 1 in a second exemplary embodiment.

In the pumping unit of FIG. 4 and FIG. 5, the elements that remain the same or function the same as in the pumping unit of FIGS. 1 through 3 are identified by the same reference numerals.

The second exemplary embodiment of FIG. 4 differs from the first exemplary embodiment of FIGS. 1 through 3 in that the indentations 38 are disposed not on the two face ends 28, 29 of the impeller 5 but rather on the two end walls 15, 16 of the pump chamber 4. The pressure equalization conduits 46 are omitted. The indentations 38, when disposed on the end walls 15, 16 of the pump chamber 4 in contrast to the disposition on the impeller 5, experience a flow through them in the direction of rotation of the impeller 5. The oblique faces 39 for hydrodynamic support should therefore each be disposed on one downstream end, in terms of the flow direction in the axial gap 20, of the indentation 38.

In the second exemplary embodiment, the indentations 38 are disposed radially inside the feed conduit 14 with respect to the pump axis 8. In the region of the lowest point 40, the indentations 38 extend for instance at least approximately parallel to the end walls 15, 16. Downstream, they extend via a rear oblique face 39, in terms of the flow direction in the axial gap 20, for hydrodynamic support with a reduction in depth, as far as a downstream groove 42 and discharge into it. Upstream, the depth of the indentation 38 decreases, either via a steplike shoulder 43 or via an upstream oblique face 39 and discharges into a groove 42 located upstream in terms of the flow direction.

The indentations 38 of the one end wall 15 of the pump chamber 4 are diametrically opposite the indentations 38 of the other end wall 16 of the pump chamber 4, for instance mirror-symmetrically relative to a middle face that is located in the middle between the end walls 15, 16 and extends parallel to them.

FIG. 6 is a sectional view with the impeller and with indentations, disposed in an end wall of the pump chamber, in accordance with the second exemplary embodiment.

In the pumping unit of FIG. 6, the elements that remain the same or function the same as in the pumping unit of FIGS. 1 through 5 are identified by the same reference numerals. 

1-10. (canceled)
 11. A pumping unit having an impeller disposed in a pump chamber and drivable to rotate by means of an actuator, the impeller comprising two face ends, an end wall of the pump chamber diametrically opposite each free end, a plurality of indentations providing hydrodynamic support in at least one of the face ends of the impeller and/or at least one of the end walls of the pump chamber, and a respective groove providing fluid communication between at least two adjacent indentations of the at least one face end and/or of the at least one end wall.
 12. The pumping unit as defined by claim 11, wherein the indentations and/or the grooves are disposed annularly.
 13. The pumping unit as defined by claim 11, wherein the indentations and/or the grooves extend in arclike, split-ringlike, oblong slot-like or similar form.
 14. The pumping unit as defined by claim 11, wherein the indentations and/or the grooves form a common ring.
 15. The pumping unit as defined by claim 11, wherein the indentations have a greater depth than the grooves.
 16. The pumping unit as defined by claim 11, wherein the indentations each have at least one face that is oblique with respect to the face ends and/or the end walls for hydrodynamic support of the impeller.
 17. The pumping unit as defined by claim 16, wherein the at least one oblique face, when the indentations are disposed on the impeller, is each provided on a trailing end of the indentation relative to a direction of rotation of the impeller.
 18. The pumping unit as defined by claim 16, wherein the at least one oblique face, when the indentations are disposed on the end walls of the pump chamber, is each provided on a downstream end of the indentation.
 19. The pumping unit as defined by claim 6, wherein the indentations each have a lowest point that extends parallel to the at least one face end and/or end wall.
 20. The pumping unit as defined by claim 11, wherein the indentations of one face end of the impeller are diametrically opposite the indentations of the other face end of the impeller mirror-symmetrically relative to a middle face, and the indentations that are diametrically opposite mirror-symmetrically are joined together via a pressure equalization conduit. 